Cannabis is a genus of flowering plants in the family Cannabaceae. Three species may be recognized (Cannabis sativa, Cannabis indica and Cannabis ruderalis). Cannabis spp. contains a highly complex mixture of compounds, up to 568 unique molecules identified to date (Pertwee, R. G. e., Handbook of cannabis. Oxford University Press: Oxford, 2014). Cannabinoids are the most noteworthy compounds found in Cannabis spp. Among these compounds, Δ9-tetrahydrocannabinol (Δ9-THC), cannabinol (CBN), and cannabinodiol (CBDL) are known to be psychoactive (Pertwee, R. G. e., Handbook of cannabis. Oxford University Press: Oxford, 2014). Other cannabinoids such as cannabidiol (CBD), which is a non-psychoactive compound, exert their physiological effects through a variety of receptors including adrenergic and cannabinoid receptors (Pertwee, R. G. e., Handbook of cannabis. Oxford University Press: Oxford, 2014). Cannabinoid receptors (CB1 and CB2) belong to G-protein coupled receptors (GPCRs) (Cottone, E.; Pomatto, V.; Cerri, F.; Campantico, E.; Mackie, K.; Delpero, M.; Guastalla, A.; Dati, C.; Bovolin, P.; Franzoni, M. F. Cannabinoid receptors are widely expressed in goldfish: molecular cloning of a CB2-like receptor and evaluation of CB1 and CB2 mRNA expression profiles in different organs. Fish Physiology and Biochemistry 2013, 39 (5), 1287-1296). Phytocannabinoids produced by Cannabis spp. plants as well as endocannabinoids produced in our body bind to these receptors. Patients consume medical cannabis for the treatment of or seek relief from a variety of clinical conditions including pain, anxiety, epileptic seizures, nausea, and appetite stimulation (Galal, A. M.; Slade, D.; Gul, W.; El-Alfy, A. T.; Ferreira, D.; Elsohly, M. A. Naturally occurring and related synthetic cannabinoids and their potential therapeutic applications. Recent patents on CNS drug discovery 2009, 4 (2), 112 and Downer, E. J.; Campbell, V. A. Phytocannabinoids, CNS cells and development: A dead issue? Phytocannabinoids have neurotoxic properties. Drug and Alcohol Review 2010, 29 (1), 91-98). It is also known that cannabinoids and endocannabinoids affect the development and maturation of neural cells in early life (Downer, E. J.; Campbell, V. A. Phytocannabinoids, CNS cells and development: A dead issue? Phytocannabinoids have neurotoxic properties. Drug and Alcohol Review 2010, 29 (1), 91-98). Cannabinoid-like compounds isolated from flax have also shown anti-inflammatory properties (Styrczewska, M.; Kulma, A.; Ratajczak, K.; Amarowicz, R.; Szopa, J. Cannabinoid-like anti-inflammatory compounds from flax fiber. Cellular & Molecular Biology Letters 2012, 17 (3), 479-499).
Most cannabinoids are concentrated in a viscous resin produced in structures of the cannabis plant known as glandular trichomes. At least 113 different cannabinoids have been isolated from the cannabis plant, the most common being Δ9-tetrahydrocannabinolic acid (Δ9-THC-A) which is the non-active precursor of the psychoactive Δ9-tetrahydrocannabinol (Δ9-THC).
Δ9-THC-A is found in variable quantities in fresh, undried cannabis, but is progressively decarboxylated to Δ9-THC with drying, and especially under intense heating such as when cannabis is smoked or cooked into cannabis edibles.
Δ9-THC is not the only substance obtained from cannabis with therapeutic benefits to people. For example, studies have shown that cannabidiol (CBD), another major constituent of some strains of cannabis, has been found to be anxiolytic and to have antipsychotic properties, and may be neuroprotective in humans.
FIG. 1A shows chemical structures of six major cannabinoids present in or which can be obtained from cannabis: Δ9-THC, Δ9-THC-A, Δ8-THC, cannabinol (CBN), Δ2-CBD and cannabidiolic acid (Δ2-CBD-A). FIG. 1B shows the cannabinolic acid synthase pathway of cannabigerolic acid (CBGA) to cannabidiolic acid (CBDA), tetrahydrocannabinolic acid (THCA) and cannabichromenic acid (CBCA), which can all be decarboxylated to active cannabinoid forms. In some cases, the non-decarboxylated cannabinoids may also have therapeutic properties.
Decarboxylation is a chemical reaction that releases carbon dioxide and generates neutral cannabinoids. In one example in cannabis, the non-psychoactive Δ9-THC-A can be converted to psychoactive Δ9-THC by decarboxylation.
There is a need to produce a cannabis resin comprising cannabinoids that are decarboxylated. The cannabis resins or extracts known in the art may not be consistently and fully decarboxylated and comprise significant proportions of THCA and CBDA. For example, see WO 2014/159688. The cannabis extracts or resins of the art are for use, for example, in vaporization, infusion into edible matrices, and inhalation via electronic inhalation devices. Accordingly, the extracts and resins of the art comprise predominantly THCA and/or CBDA, as opposed to their decarboxylated counterparts (THC and CBD respectively), and it is only after heating the extracts and resins via vaporization or cooking in edible matrices that decarboxylation occurs (i.e. only after heating the extracts and resins that the cannabinoids are decarboxylated into their active forms). As the cannabis resins of the present disclosure comprise decarboxylated therapeutically active cannabinoids, they may be used directly. For example, the cannabis resins of the present disclosure may be used directly in therapy or used to develop various cannabis formulations for pharmaceutical products that do not need to be further heated (i.e. decarboxylated) into therapeutically active forms.
Many people may be reluctant to use cannabis (either as a medicine or natural health product) if it has to be “smoked” or heated (i.e. “vaping”). This may be because there are negative perceptions to smoking and vaping, especially in the older generation. Many people may be more accepting of cannabis if it is in a form that is more conventional (i.e. tablet form, or other conventional forms of medicine). In order, to produce conventional forms of cannabis for use as a medicine or natural health product, the cannabinoids in the product must be decarboxylated.
There is also a need to develop an efficient method of extracting and decarboxylating cannabinoids from cannabis. 
To date the simplest mechanism to perform decarboxylation of cannabinoid acids is by heating. Other processes of decarboxylation require toxic solvents. In these systems, a distillation process such as fractional distillation may be employed to separate the organic solvents from the cannabis extract after decarboxylation.
In addition to decarboxylation, extraction of cannabinoids from the plant material is required. Extraction is most often done prior to decarboxylation. Mechanisms of extraction of cannabinoids such as Δ9-THCA and CBDA from cannabis that are known include sonication, reflux (Soxhlet) extraction and supercritical fluid extraction (SFE). For example, U.S. Pat. No. 9,044,390 describes a fractional SFE process of contacting cannabis plant material with a supercritical fluid solvent system at a pressure between about 750 psi and 25,000 psi, and at a temperature between about −15° C. and 200° C.
With the rise in the authorized use of cannabis for medical, therapeutic and recreational purposes, there is an increasing need for a reproducible method for obtaining a consistent active cannabinoid-comprising resin with known efficacy and to optimize production and recovery of active decarboxylated cannabinoids. With increasing demand and potential uses, there is also a need for a method that can be easily scaled-up for manufacture of commercial pharmaceutical preparations, natural health product preparations or recreational use preparations.